Evaluating patients with suspected hypoxic respiratory failure 2

1
Key messages from the British Thoracic Society
Emergency Oxygen Guideline
This presentation was last updated on 1-10-09
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Oxygen - there is a problem

• Published audits have shown
• Doctors and nurses have a poor understanding of
  how oxygen should be used
• Oxygen is often given without any prescription
• If there is a prescription, it is unusual for the
  patient to receive what is specified on the
  prescription

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Oxygen - there was a disagreement

• Chest Physicians
• Intensivists / Anaesthetists
• Emergency Medicine / AE clinicians
• Ambulance teams

4
Time to do something!

• The British Thoracic Society, together with 21
  other Societies and Colleges has produced a
  multi-discipline Guideline for emergency oxygen
  use.
• This Guideline covers most aspects of emergency
  oxygen use in pre-hospital care and in emergency
  hospital care for adults (excludes NIV and IPPV)

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British Thoracic Society Guideline for
emergency oxygen use in adult patients Endorsed
by Association of Respiratory Nurse
Specialists Association for Respiratory
Technology and Physiology British Association for
Emergency Medicine British Cardiovascular
Society British Geriatric Society British
Paramedic Association Chartered Society of
Physiotherapy General Practice Airways Group
(GPIAG) Intensive Care Society Joint Royal
Colleges Ambulance Liaison Committee Resuscitation
Council (UK) Royal College of Anaesthetists Royal
College of General Practitioners Royal College
of Midwives Royal College of Nursing Royal
College of Obstetricians and Gynaecologists
(approved) Royal College of Physicians (London,
Glasgow, Edinburgh) Royal Pharmaceutical Society
of Great Britain Society for Acute
Medicine ODriscoll BR. Howard LS, Davison AG.
Thorax 2008 63 Suppl VI
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Basis of the BTS guideline Prescribing by
target oxygen saturation Keep it
normal/near-normal for all patients except
pre-defined groups who are at risk from
hypercapnic respiratory failure
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What is normal and what is dangerous?
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Normal Range for Oxygen saturation
Normal range for healthy young adults is
approximately 96-98 (Crapo AJRCCM,
19991601525) SLIGHT FALL WITH ADVANCING AGE A
study of 871 subjects showed that age gt 60 was
associated with minor SpO2 reduction of 0.4
Witting MD et al Am J Emerg Med 2008 26
131-136 An audit in Salford and Southend showed
mean SpO2 of 96.7 with SD 1.9 in 320 stable
hospital patients aged gt70 ODriscoll R et al
Thorax 2008 63(suppl Vii) A126

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Effects of sudden hypoxia(e.g Removal of oxygen
mask at altitude or in a pressure chamber)

• Impaired mental function Mean onset at SaO2 64
  No evidence of impairment above 84 saturation
• Loss of consciousness at mean saturation of 56
• Test Pilots in decompression chambers do not
  experience breathlessness when the oxygen tension
  is lowered
• Akero A et al Eur Respir J. 2005 25725-30
• Cottrell JJ et al Aviat Space Environ Med. 1995
  66126-30
• Hoffman C, et al. Am J Physiol 1946, 145,
  685-692

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What happens at 9,000 metres (approximately
29,000 feet) it depends
Atmospheric pO2 6.2 kPa (lt 1/3 sea level pO2)
PaO2 3.3 kPa Arterial Oxygen Saturation 70
SUDDEN
ACCLIMATISATION
Passengers unconscious in lt60 seconds if
depressurised
Everest has been climbed without oxygen
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Why is oxygen used?
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Aims of emergency oxygen therapy

• To correct or prevent potentially harmful
  hypoxaemia
• To alleviate breathlessness (only if hypoxaemic)
• Oxygen has no effect on breathlessness if the
  oxygen saturation is normal

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Fallacies regarding Oxygen Therapy Routine
administration of supplemental oxygen is useful,
harmless and clinically indicated

• Little increase in oxygen-carrying capacity
• Renders pulse oximetry worthless as a measure of
  ventilation
• May prevent early diagnosis specific treatment
  of hypoventilation
• This guideline only recommends supplemental
  oxygen when SpO2 is below the target range
• or in critical illness or CO Poisoning
• John B Downs MD Respiratory care 200348611-20

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Oxygen therapy is only one element of
resuscitation of a critically ill patient

• The oxygen carrying power of blood may be
  increased by
• Safeguarding the airway
• Enhancing circulating volume
• Correcting severe anaemia
• Enhancing cardiac output
• Avoiding/Reversing Respiratory Depressants
• Increasing Fraction of Inspired Oxygen (FIO2)
• Establish the reason for Hypoxia and
• treat the underlying cause (e.g
  Bronchospasm, LVF etc)
• Patient may need, CPAP or NIV or Invasive
  ventilation

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Defining safe lower and upper limits of oxygen
saturation
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What is the minimum arterial oxygen level
recommended in acute illness

• Target oxygen
  Saturation
• Critical care consensus guidelines
  Minimum 90
• Surviving sepsis campaign
  Aim at 88-95
• But these patients have intensive levels of
  nursing monitoring
• This guideline recommends a minimum of 94 for
  most patients combines what is near normal and
  what is safe

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Exposure to high concentrations of oxygen may be
harmful

• Absorption Atelectasis even at FIO2 30-50
• Intrapulmonary shunting
• Post-operative hypoxaemia
• Risk to COPD patients
• Coronary vasoconstriction
• Increased Systemic Vascular Resistance
• Reduced Cardiac Index
• Possible reperfusion injury post MI
• Worsens systolic myocardial performance
• Oxygen therapy INCREASED mortality in non-hypoxic
  patients with mild-moderate stroke
• This guideline recommends an upper limit of
  98 for most patients. Combination of what is
  normal and safe

Harten JM et al J Cardiothoracic Vasc Anaesth
2005 19 173-5 Kaneda T et al. Jpn Circ J 2001
213-8 Frobert O et al. Cardiovasc Ultrasound
2004 2 22 Haque WA et al. J Am Coll Cardiol
1996 2 353-7 Thomaon aj ET AL. BMJ 2002
1406-7 Ronning OM et al. Stroke 1999 30
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Some patients are at risk of CO2 retention and
acidosis if given high dose oxygen

• Chronic hypoxic lung disease
• COPD
• Severe Chronic Asthma
• Bronchiectasis / CF
• Chest wall disease
• Kyphoscoliosis
• Thoracoplasty
• Neuromuscular disease
• Obesity hypoventilation

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What is a safe lower Oxygen level in acute COPD?

• In acute COPD
• pO2 above 6.7 kPa
• or 50 mm Hg
• will prevent death
• PaO2 above about 85
• (Keep SpO2 88 to allow for oximeter error and
  ensure PaO2 gt85 )

Murphy R, Driscoll P, ODriscoll R Emerg Med J
2001 18333-9
This guideline recommends a minimum saturation
of 88 for most COPD patients
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What is a safe upper limit of oxygen target
range in acute COPD ?

• 47 of 982 patients with exacerbation of COPD
  were hypercapnic on arrival in hospital
• 20 had Respiratory Acidosis (pH lt 7.35)
• 5 had pH lt 7.25 (and were likely to need ICU
  care)
• Most hypercapnic patients with pO2 gt 10 kPa were
  acidotic (equivalent to oxygen saturation of
  above 92) i.e.
  They had been given too much oxygen
• RECOMMENDED UPPER LIMITS
• Keep PaO2 below 10 kPa and
• keep SpO2 92 in acute COPD

Plant et al Thorax 2000 55550
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Recommended target saturations

• The target ranges are a consensus agreement
  by the guidelines group and the endorsing
  colleges and societies
• Rationale for the target saturations is
  combination of
• what is normal and what is safe
• Most patients 94 - 98
• Risk of hypercapnic respiratory failure 88
  92
• 
  Or patient
  specific saturation on Alert Card

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Using Target Saturation Scheme

• O2 prescribed by target saturation
  (like an Insulin BM
  sliding-scale chart)
• Oxygen delivery device and flow administered and
  changed if necessary to keep the SpO2 in the
  target range
• Target oxygen saturation prescription integrated
  into patient drug chart and monitoring

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Safeguarding patients at risk of type 2
respiratory failure

• Lower target saturation range for these patients
  (88-92)
• Education of patients and health care workers
• Use of controlled oxygen via Venturi masks
• Use of oxygen alert cards
• Issue of personal Venturi masks to high-risk
  patients

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OXYGEN ALERT CARD Name
______________________________
I am at risk of type II respiratory
failure with a raised CO2 level. Please use my
Venturi mask to achieve an oxygen
saturation of _____ to _____ during
exacerbations Use compressed air to drive
nebulisers (with nasal oxygen a 2 l/min). If
compressed air not available, limit oxygen-driven
nebulisers to 6 minutes.
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Oxygen Alert Cards and Venturi masks can avoid
hypercapnic respiratory failure associated with
high flow oxygen masks

• Oxygen alert card (and a Venturi mask) given to
  patients admitted with hypercapnic acidosis with
  a PO2 gt 10kPa.
• Patients instructed to show these to ambulance
  and AE staff.
• After introduction of alert cards
• Use of Venturi mask 63 in Ambulance
• 94 in AE
• Gooptu B, Ward L, Davison A et al. Oxygen alert
  cards and controlled oxygen masks
• Emerg Med J 2006 23636-8

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Danger of Rebound Hypoxaemia

• If you find a patient who is severely hypercapnic
  due to excessive oxygen therapy (e.g pH 7.23 Pa
  CO2 13 PaO2 35)
• Do NOT stop oxygen therapy abruptly.
• The PaCO2 is very high which causes low PAO2 due
  to the Alveolar Gas Equation (PAO2 FIO2
  PaCO2/RQ )
• If suddenly changed to air --? PAO2 20
  16.2 4 kPa ( PaO2 will be even lower)
• It is safest to step down to 35 oxygen if the
  patient is
• fully alert or call your Critical Care team
  arrive to provide mechanical ventilation if the
  patient is drowsy.

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Prescribing Oxygen
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Oxygen prescription Model for oxygen section in
hospital prescription charts
Tick if saturation not indicated
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Oxygen prescription and Administration

• Clinician (usually a doctor) prescribes oxygen by
  circling the desired oxygen saturation target
  range
• Staff use appropriate device and flow rates in
  order to maintain saturation within the target
  range

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Oxygen use in palliative care

• Most breathlessness in cancer patients is caused
  by specific issues such as airflow obstruction,
  infections or pleural effusions and the main
  issue is to treat the cause
• Oxygen has been shown to relieve dyspnoea in
  hypoxic cancer patients
• Morphine and Midazolam may also relieve
  breathlessness

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Devices
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High Concentration Reservoir Mask

• Non re-breathing Reservoir Mask.
• Critical illness / Trauma patients.
• Post-cardiac or respiratory arrest.
• Delivers O2 concentrations between 60
  80 or above
• Effective for short term treatment.

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Nasal Cannulae

• Recommended in the Guideline as suitable for most
  patients with both type I and II respiratory
  failure.
• 2-6L/min gives approx 24-50 FIO2
• FIO2 depends on oxygen flow rate and patients
  minute volume and inspiratory flow and pattern of
  breathing.
• Comfortable and easily tolerated
• No re-breathing
• Low cost product
• Preferred by patients (Vs simple mask)

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Simple face mask (Medium concentration,
variable performance)

• Used for patients with type I respiratory
  failure.
• Delivers variable O2 concentration between 35
  60.
• Low cost product.
• Flow 5-10 L/min
• Flow must be at least 5 L/min to avoid CO2
  build up and resistance to breathing
• (although packaging may say 2-10L)

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Venturi or Fixed Performance Masks
Aim to deliver constant oxygen concentration withi
n and between breaths. 24-40 Venturi Masks
operate accurately A 60 Venturi mask gives 50
FIO2 With TACHYPNOEA (RR gt30/min) the
oxygen supply should be increased by 50
Increasing flow does not increase oxygen
concentration
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Operation of Venturi valve

Air
O2 Air
O2
Air
For 24 Venturi mask, the typical oxygen flow of
2 l/min gives a total gas flow of 51 l/minFor
28 Venturi mask, 4 l/min oxygen flow, gives a
total gas flow of 44 l/min(Table 10.2)
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Oxygen Flow MeterThe centre of the ball
indicates the correct flow rate.
This diagram illustrates the correct setting of
the flow meter to deliver a flow of 2 litres per
minute
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What device and flow rate should you use in each
situation?
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• Standard Oxygen Therapy 1960s-2008

Acute Patients
Stable Patients
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• Oxygen therapy 2008 onwards

Selected COPD patients
Critical illness
Most patients
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Many patients need high-dose oxygen to normalize
saturation

• Severe Pneumonia
• Severe LVF
• Major Trauma
• Sepsis and Shock
• Major atelectasis
• Pulmonary Embolism
• Lung Fibrosis
• Etc etc etc

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BTS Recommendations
Prescribe to target
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Prior to Blood Gas Analysis
Is the patient critically ill?
Yes treat with reservoir or bag-valve mask
No
Is the patient at risk of hypercapnic respiratory
failure?
No is SpO2 lt 85?
Yes aim for SpO2 88-92 or level on alert card
pending ABG
No aim for SpO2 94-98
Start with 24 or 28 Venturi mask
Start with nasal cannulae (2-6 l/min) or face
mask (5-10 l/min)
Critical illness is defined as cardiopulmonary
arrest, shock, major trauma head injury,
near-drowning, anaphylaxis, major pulmonary
haemorrhage and carbon monoxide poisoning.
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Yes aim for SpO2 88-92 or level on alert card
pending ABG
Reduce FiO2 if SpO2 gt 92
Perform Arterial Blood Gases
pH lt 7.35 and PaCO2 gt 6.0 kPa or patient tiring
Consider NIV or IPPV
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Yes aim for SpO2 88-92 or level on alert card
pending ABG
Reduce FiO2 if SpO2 gt 92
Perform Arterial Blood Gases
pH lt 7.35 and PaCO2 gt 6.0 kPa or patient tiring
pH gt 7.35 and PaCO2 gt 6.0 kPa
Maintain SpO2 88-92 with lowest FiO2
Consider NIV or IPPV
Repeat ABG in 30-60 mins
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Yes aim for SpO2 88-92 or level on alert card
pending ABG
Reduce FiO2 if SpO2 gt 92
Perform Arterial Blood Gases
PaCO2 lt 6.0 kPa
pH lt 7.35 and PaCO2 gt 6.0 kPa or patient tiring
pH gt 7.35 and PaCO2 gt 6.0 kPa
Maintain SpO2 94-98 with lowest FiO2 unless
previous NIV or IPPV
Maintain SpO2 88-92 with lowest FiO2
Consider NIV or IPPV
Repeat ABG in 30-60 mins
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• Titrating Oxygen up and down.
• This table below shows APPROXIMATE conversion
  values.
• Venturi 24 (blue) 2-4l/min OR
  Nasal specs 1L
• Venturi 28 (white) 4-6 l/min
  OR Nasal specs 2L
• Venturi 35 (yellow) 8-10l/min
  OR Nasal spec 4L
• Venturi 40 (red)10-12l/min
  OR Simple face mask 5-6L/min
• Venturi 60 (green) 15l/min OR
  Simple face mask 7-10L/min
• Reservoir mask at 15L oxygen flow
• seek medical advice

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Monitoring patients

• Oxygen saturation and delivery system should be
  recorded on the monitoring chart.
• Delivery devices and/or flow rates should be
  adjusted to keep oxygen saturation in target
  range.

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Model for respiratory section of observation chart
Codes for recording oxygen delivery on
observation chart A Air. (Patient not
requiring oxygen therapy) AX Measurement on
air for a patient who is on PRN Oxygen therapy AW
Measurement on air for a patient who is being
weaned off oxygen but not yet discontinued on
chart N Nasal Cannulae SM Simple
mask V24 Venturi 24 V28 Venturi 28 V35
Venturi 35 V40 Venturi 40 V60 Venturi
60 H28 Humidified oxygen at 28 (Quatro or
similar device) (also H 35, H40, H60) RM
Reservoir Mask TM Tracheostomy Mask CP
Patient on CPAP system NIV Patient on NIV
system OTH Other device All changes to oxygen
delivery systems must be initialled by a
registered nurse or equivalent If the patient is
medically stable and in the target range on two
consecutive rounds, report to a registered nurse
to consider weaning off oxygen (unless the
oxygen prescription is part of a timed protocol
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From the BTS Emergency Oxygen Guideline To the
patient

• Guideline agreed by the whole UK medical, nursing
  and AHP community (endorsed by 21 Colleges and
  Societies)
• Medical and Nurse/Physio Champions in every
  Hospital Trust
• New prescription charts and monitoring charts in
  every hospital
• Training packages on BTS website
• NPSA Rapid Response Report September 2009
• Audit tools on BTS website www.brit-thoracic.org.u
  k

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Summary

• Prescribe oxygen to a target saturation for each
  group of patients
• 94 - 98 for most adult patients
• 88 - 92 if risk of hypercapnia (or
  patient-specific target on alert card)
• Administer oxygen to achieve target saturation
• Monitor oxygen saturation and keep in target
  range
• Taper oxygen dose and stop when stable
• Audit your practice
• All information on www.brit-thoracic.org.uk